I've set up mail servers many times over many decades and it's not as hard as a lot of people think. For a reasonably secured and maintained personal server, you'll have to learn about SPF, DMARC, and do more detailed DNS setup than you do to get a quick website up, but once up, everything should go well... so long as you and your family behave.

For businesses, especially those with enthusiastic marketing teams, it's harder because all it takes is a a bug in some transactional email code, or a bad email from a well meaning sales rep to some email list from a "digital marketing" forum to completely wreck your server's reputation.